The position of the sun is not as simple a problem as you might think. Go to www.analemma.com as a start. Did you know that the longest day of the year has neither the earliest sunrise nor the latest sunset? For your learning fun, just browse for "Solar Position." It is tempting to say our collecter position is close and that's good enough, but in this day when engineers try to get energy efficiency on the order of microwatts, we want all the energy we can attain. I hope the other suggested uses for the multiplexing project do not get lost in the discussion.
The solar trackers that I have seen all had a much simpler tracking system. The rough aiming was done with a simple timer and the fine control done with 4 photodiodes placed in the sided of an x shaped metal or plastic extrusion that extended 3or 4 inched outward, and shaded the diodes that were pointed fathest away from the sun. The tracker moved towards whichever diode had the most light on it. This was all done with analog circuitry.
Hm NREL.GOV has a C source code available to the public to track the sun using time stamp and a single microcontroller. The only problem is the feedback loop. LVDT's or RVDT's can get expensive so it might be simpler to have an array of 10cent phototransistors with a microcontroller I don't know? And have a direct feedback loop between light intensity and position of sensor (assuming that sensor is in the same plane as your collector (dish or trough is fine). as to this being a non-problem I disagree. Current systems (reflector and aim mechanism) are way too expensive. It is roughly 200% of the current competing costs. It's hard to invest in solar because of the initial investment. I think cheaper ways to solve this problem are always a big plus.
This is really cool. However, since when did the position of the sun become unpredictable requiring us to "find" it. By the way - you could also look up "fearlessthinker" on youtube. He has built a similar sun tracker.
This is indeed a clever solution to a non-problem. We would really need it if the sun behaved like an aerobatic airplane. In actuality it "moves across the sky" at a reliable 15 deg/hour, so a simple clockwork or synchronous-motor heliostat is perfectly adequate. Even if there were a small aiming error, the derivative of the cosine is very weak in the vicinity of 0 deg, so your solar panels would still produce full output.
Jerald, your project is wonderful and stimulating on a number of levels. It is simple and elegant, from the design, to the selection of microcontroller for your purpose, to your use of multiplexing. Perhaps I have missed something, but is source code available for this project?
Thank you so much for sharing this excellent design.
Nancy, Microchip provides a variety of cool PIC micrcontrollers and tons of great app notes and source code examples. I've used them in several projects and the ease in which to get them running is truly amazing. This project is just one of several examples of how microcontroller technology can easily be implemented. Great project idea!
Your question is exactly the one I asked when I started the project.
Their methods are probably proprietary but I believe most of them would use the brute force method of calculating the sun's position. If one searches for solar position calculations, one finds that the calculation is far from simple. While C code is available free online, it would take a microcontroller that supports a multiple precision instruction set, an input of latitude/longitude, current time, real time clock, look-up trig tables, etc. While my approach is not purely minimalist, I wanted my device to just look up and say, "Where's the sun?"
I think this is a great project - very useful for efficient collection of solar energy! I particularly like PICs for these types of projects - they are so versatile and just plain fun. The inexpensive programmers that Microchip sells don't break the bank either and their MPLAB IDE is free and very user friendly. Great job!
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